For the millions of people across the world classified as blind, there may be a new form of treatment that could either see their sight returned, or give them what they never had before. In a paper published to Nature Biomedical Engineering, researchers from Ecole Polytechnique Fédérale de Lausanne (EPFL) described a new intraneural electrode called OpticSeline.

This implant is potentially revolutionary with the ability to stimulate the optic nerve to send images to the brain while bypassing the eyeball entirely. Silvestro Micera of EPFL was one of the researchers working on this project and has also done work in hand prosthetics for amputees using similar electrodes.

“We believe that intraneural stimulation can be a valuable solution for several neuroprosthetic devices for sensory and motor function restoration. The translational potentials of this approach are indeed extremely promising,” he said.

The implant is designed to make use of phosphenes, the sensation of seeing light in the form of white patterns but without seeing the light directly. Previous strategies to treat blindness have included retinal implants, but only a tiny fraction of the world’s blind population qualify for them.

OpticSeline electrode array for intraneural stimulation of the optic nerve, developed at EPFL. Image: EPFL/Markus Ding

A good start

Brain implants designed to stimulate the visual cortex have also been used, but are considered risky. In contrast, the EPFL researchers said this intraneural solution minimises risk since the optic nerve and pathway to the brain are often intact.

Other previous EPFL attempts to stimulate the optic nerve in a similar way back in the 1990s proved unsuccessful as the type of electrodes they used tended to move around, becoming unstable and leaving the patient struggling to see clear images.

The OpticSeline, however, has shown itself in testing in mice to be stable and less likely to move around once implanted as the electrodes pierce the nerve. To measure this success, the researchers delivered electric current to the optic nerve via the implant and measured the brain’s activity in the visual cortex.

Using an algorithm to decode the cortical signals, they could see that each stimulating electrode induces a specific and unique pattern of cortical activation, suggesting that intraneural stimulation of the optic nerve is selective and informative.

This new OpticSeline method uses 12 electrodes in mice, but a human version would require between 28 and 60 electrodes. While not returning sight entirely, the researchers added, it would be enough to provide a visual aid for daily living.